1. Field of the Invention
The present invention concerns an orthodontic appliance and, more specifically, it relates to an improved structure of a bracket used in such an appliance for correcting misaligned teeth.
2. Description of the Prior Art
A person's teeth greatly influence his or her looks and facial features, in addition to their important role in chewing food. Therefore, recently, the number of people, especially young women, who worry about their misaligned teeth and thus become negative in personal relationship has been increasing. Most patients consulting orthodontists complain about their appearance.
A typical orthodontic appliance comprises a plurality of brackets to be fixed to the surfaces of teeth and a metal wire for connecting those brackets to each other along the direction of a set of teeth.
As the bracket used for the appliance of this type, there has been known a so-called "edgewise bracket" comprising a base plate and a pair of wire supports which are disposed along the two lateral ends of the base plate and which define a square groove recessed laterally into the center of each support.
For correcting misaligned teeth by using the orthodontic appliance described above, for instance, a first premolar just behind a canine is extracted to make room and then the bracket is fixed to the surface of each of the teeth. Then a wire is laterally extended under tension through the groove of each bracket and both ends of the wire are fixed to a pair of first molars. Further a rubber band is stretched between the brackets appended to the canine and the first molar.
Thus, the bracket fixed to the tooth and the wire move slidingly relative to each other to correct the misaligned teeth with lapse of time.
However, correction of the misaligned teeth actually takes a considerable period of time, because the relative movement between the wire support of the bracket and the wire is not smooth.
Incidently, since the appearance of a patient with brackets on his teeth is not very good, it is desirable to shorten the period of tooth correction.
Considering that one of the major factors which extends the correction period is friction between the recessed grooves and the connection wire, the present inventor has studied how to reduce this friction.